Conventional systems for applying potent cosmetically active materials, such as perfumes, to the body, especially onto the skin, rely on solvent dilution to deliver sufficiently low concentrations of these actives. The presence of the solvent, however, may limit the effectiveness of the active material, for example by physical and/or chemical interactions, particularly on storage, and also restricts the range of cosmetic actives which can be delivered by these known systems.
Hitherto, perfumes for example are generally delivered from pressurized containers and in the form of a solution of the perfume active in a suitable solvent such as an alcohol. Such delivery systems are inefficient, bulky, heavy and expensive. A further problem associated with these known systems, as well as being noisy to use and having poor sensory appeal, i.e. generating cold, wet sprays, is that there is significant waste through loss of the active material to the atmosphere which also results in unwanted atmospheric mists and contamination to the user's eyes and other body parts, which may present respiratory or other health problems to the user. This is particularly problematic in shops and department stores for example, where many perfume sprays are frequently tested by potential customers, giving rise to considerable atmospheric pollution and waste. The use of aerosol propellants which are volatile organic compounds are also now well recognised as being environmentally unfriendly, possibly hazardous to health and indeed are being legislated against in many countries of the world.
In a very different technical field, the principle of electrostatic spraying of liquid and solid materials is also known. In this technique a formulation to be sprayed is raised to a high electric potential in a spray nozzle to cause the formulation to atomise as a spray of electrically charged droplets. Such electrically charged droplets seek the closest earthed object to discharge their electric charge, and this can be arranged to be the desired spray target. Hitherto, electrostatic spraying techniques have been proposed principally for only large-scale industrial and agricultural applications, especially for delivering reactive materials like paints, adhesives and other surface coatings, as well as large-scale delivery of pesticides and other agricultural or agrochemical formulations. Examples of disclosures in this field include GB-A-1393333, GB-A-1569707, GB-A-2092025, EP-A-029301, EP-A-253539 and WO-A-85/00761, the contents of which disclosures are incorporated herein by reference.
More recently, there have been a small number of proposals for utilising the known principle of electrostatic spraying for delivering particular materials in specific applications other than those mentioned above.
EP-A-224352 suggests the use of an electrostatic sprayer for delivering a pharmaceutically active agent to the eye, to replace conventional ocular treatment using eye drops.
JP-A-56-97214 (dating from 1981) suggests the use of electrostatic spraying for applying a granular (i.e. solid particles of) colouring material to hair to effect surface coating thereof.
Also to be mentioned, though of less relevance, is U.S. Pat. No. 4,776,515, which proposes an electrodynamic fine particle negative ion generator adapted to spray various liquids, particularly water, but possibly also alcohol, perfume, ammonia, liquid medications and surfactants. The object of the disclosed system is to provide an ozone-free mist of negatively ionised liquid particles, (which presupposes that the material to be sprayed is ionizable), and the mist that is produced instantly disperses into an open area in which the apparatus is operated, e.g. a room, so that a far-reaching, uniform aerosol is generated which has particular applicability for large public areas such as hospitals, restaurants and offices. Clearly, this system is unsuitable for small-scale personal use and in many of its objects goes directly against the principles upon which a solution to the above mentioned prior art problems must be founded.